Beetle threatens California Navel exports to Korea

The California citrus industry is in fast-track mode to enact solutions to keep Fuller rose beetle (FRB) eggs out of Navel orange shipments exported next year to Korea.

Starting in January, a failure to do so could bring California Navel shipments to Korea to a halt or reduce shipment levels, according to Jim Cranney, president of the California Citrus Quality Council[4] (CCQC) in Auburn, Calif.

Korea is the top importer of California Navels, valued at about $213 million to the California industry annually. On average, California ships about 10 million cartons of Navels to Korea each year.

About 30 percent of all California-grown citrus is exported. This represents about 40 percent of the industry’s annual income.

Cranney says the problem maker is the eggs of the Fuller rose beetle, Naupactus (Asynonychus) godmaniand, which are potential hitchhikers in California Navel shipments to Korea. The beetle likes to lay its eggs under the calyx (button) on citrus.

According to UC IPM Online, the FRB adult is a brown, flightless snout beetle with one generation of offspring per year. The adult pest emerges from the soil year-round and climbs into the tree via branches or the trunk. It causes minor damage to the Navel orange tree leaves and roots but, no damage to the fruit. There is no threat to human health.

Currently, Korea fumigates imported California Navels with methyl bromide upon arrival at Korean ports to kill any possible FRB eggs in the shipment. Korea fears that if the pest was introduced in Korea it could become a problem on crops other than citrus, where the insect could cause more serious crop damage.

Korea wants to eliminate methyl bromide exposure to port workers and the logistical complications which fumigation causes in busy port facilities. Some governments around the world are also voluntarily reducing the use of methyl bromide due to environmental concerns.

Starting in 2014, Korea is likely to expect the California citrus industry to treat Navels for FRB before shipping the fruit to Korea.

The country’s request was shared with California citrus leaders several years ago. Korea asked that California work quickly to institute the change. The change is likely to become effective next year.

“The elimination of Fuller rose beetle eggs on Korea-bound Navel shipments could be the responsibility of the California citrus industry effective in 2014,” said Jim Cranney, president of the California Citrus Quality Council (CCQC), Auburn, Calif.

The CCQC’s mission is to solve issues brought about by domestic or international regulatory action. Cranney says that except for the possible introduction of Huanglongbing, the Fuller rose beetle-Navel issue is the most important citrus industry challenge in California.

“Effective next year, a single Fuller rose beetle egg found in a shipment bound for Korea could cause the shipment to be rejected before it leaves California,” Cranney said. “An interruption in trade could deal a major financial blow to the California citrus industry.”

It is unknown at this point whether Korea will insist on the complete removal of blanket fumigation in Korea or if a potential transition period might be negotiated.

No crystal ball

Many of the mitigation measures needed to control FRB need to be in place before the season begins.

Given Korea’s previous efforts to eliminate blanket fumigation over the last two years, it creates uncertainty about its continued viability and the ability of USDA negotiators to maintain the fumigation.

The USDA Animal and Plant Health Inspection Service and Korean quarantine officials will negotiate the final terms of the issue this summer.

“We really need to take steps to control the pest in California,” Cranney said with urgency in this voice.

“No one has a crystal ball and we don’t know for sure how this issue will be resolved. From everything we have heard from APHIS, it will be a very heavy lift to maintain blanket fumigation in Korea.”

CCQC, researchers, government leaders, and other organizations are working hand-in-hand to develop effective FBR control techniques to ensure the California-Korea pipeline remains open.

There is not a single solution right now, Cranney says. The industry has a toolbox of methods to greatly reduce beetle and egg numbers.

“I think we have a good set of options in place,” Cranney said. “However right now, we cannot guarantee that any of these tools by themselves will eliminate every single insect or egg.” The tools are designed for implementation in Navel orange groves and packinghouses.

The adult FRB is a crawling insect, which moves from the soil into the tree wherever the two come in contact – low limbs touching the ground and the tree trunk. Once in the tree, the FRB adult lays its eggs under the calyx; the area where the stem attaches to the fruit.

FRBs feed along the citrus leaf margin creating sharp, ragged notches but cause no damage to the actual fruit.

The CCQC is collaborating with University of California entomologists Joseph Morse and Beth Grafton-Cardwell to find solutions to keep the insects out of the tree. Morse recommends skirt pruning branches to keep the limbs from touching the ground.

For FRBs which prefer to climb up the trunk, Morse’s solution is to apply the Brigade WSB, with the insecticide active ingredient bifenthrin, on the trunk using a wand sprayer to keeps the pesticide from reaching the fruit.

The problem though is the current product label maximum rate for Brigade WSB is two applications at one-quarter pound each (one-half pound annually); possibly not enough for an effective kill rate or enough applications to kill the adults during peak emergence from July through October.

The CCQC is working with FMC, the product manufacturer, and the California Department of Pesticide Regulation to increase the maximum label rate to four applications at the same rate (1-pound total annually). Morse says this rate offers improved FRB control.

Cranney says bifenthrin is highly effective against FRB adults, but is not 100-percent effective.

“Korea doesn’t want 95-percent control. Korea wants 99.9999-percent control. We don’t have 100 percent control of the Fuller rose beetle eggs with this method right now, but it is the best option currently available.”

Farm tactics and fumigation

Another insecticidal possibility is under review by Beth Grafton-Cardwell, director of the Lindcove Research and Extension Center, Exeter, Calif. Grafton-Cardwell has determined that the products Sevin, Actara, and Kryocide provide fairly good, but not a perfect kill of the FRB.

In combination with skirt pruning and trunk treatments, the foliar treatments could be used to kill adults which find a way onto the foliage.

Additionally, Cranney says some of the more effective foliar pesticides lack maximum residue levels (MRLs) for product use in some global markets. He says gaining MRLs for insecticides is a very time-consuming process.

Morse and Grafton-Cardwell have written a detailed FRB article which will appear in the March-April issue of Citrograph magazine, published by the California Citrus Research Board[6].

Cranney says ethyl formate kills about 85 percent of FRB eggs. The CCQC is seeking full registration of the product which could be approved by this fall.

Spencer Walse of USDA-ARS[8] in Parlier, Calif., is conducting research on the active ingredient phosphine, a relatively toxic fumigant which Cranney says would likely be used in a fumigation chamber or with a dedicated tarping system.

Overall, Cranney says FRB control could be achieved through a combination of on-farm tactics and fumigation, but this will depend on population levels in individual groves and whether the fumigants can be registered in time for use next season.

Nearly all of the available options for FRB control are new tactics so the industry has very little experience on how the products will work under field conditions.

Cranney says the CCQC is also concerned about the cost of these measures.

“We have a set of tools, when used in combination, can probably do the job,” the citrus leader said. “The industry faces a huge learning curve. The challenge over the next few years is to determine which products are the best tools for the job and how to use them.”

The next step is for the California citrus industry to execute the plan.

“I am optimistic that Fuller rose beetle egg control efforts will keep California Navel orange trade flowing with Korea, but it will require more costs and efforts to get there,” Cranney concluded.

The University of California will conduct a Fuller rose beetle field day April 22 at the Lindcove Center from 1 to 3 p.m. For more information, call (559) 592-2408.